The present invention relates in general to cylinder type key locks, and more particularly to key-operated rotary plug cylinder locks having rotary disc type tumblers and having special provisions for protecting the same against detection of the distinctive key contour or combination surface by picking probes or reading probes or the like and otherwise enhancing protection of the lock against unauthorized entry.
One of the common types of key locks which have come into wide use is the type known as a cylinder lock. Conventional cylinder locks normally comprise a relatively fixed housing forming the lock body or casing having a cylindrical bore opening through the front surface of the lock body which rotatably houses a rotating cylinder or plug assembly. The rotatable cylinder or plug assembly has a key way or key slot opening through the front surface of the cylinder or plug and extending over most of the axial length thereof, as well as one or more resiliently urged tumblers formed of rotatable or slidable members which normally occupy positions crossing the sheer zones or interfacial zones at boundaries between the rotatable cylinder or plug and the outer body or casing preventing rotation of the plug relative to the casing. When a key of proper contour or combination surface is inserted in the key way or key opening in the cylinder or plug, the contoured key surface aligns the resiliently urged tumblers in such a way that a parting line, either of the tumbler members or of some other locking member coactive with the tumbler members, is brought into coincidence with the interfacial plane or the arcuate peripheral surface of the plug at the sheer zone, so that when all of the resiliently urged tumblers are properly aligned by the contoured key surface, rotational force applied to the key permits the plug to turn through the normal motion involved in moving the lock from a locked to an unlocked condition.
Due to conditions which arise in the construction of the lock parts under normal manufacturing tolerances, it has been possible in cylinder locks which are not provided with special pick-resistant features, to achieve unauthorized operation of the lock by such picking techniques as inserting a picking tool into the keyway and exerting a torque on the plug so that with careful movement of the plug in selected directions, the resiliently urged tumbler first placed in compression by torquing the plug is aligned by the pick for clearance, at which point the plug rotates a minute degree to bring the next resiliently urged tumbler into similar compressed condition and it is then aligned by the pick for clearance, and this succession of operations is repeated until all the tumblers have been aligned to permit the plug or cylinder to be rotated.
One of the most common types of cylinder locks is the pin tumbler type cylinder lock, wherein segmented tumbler pins formed of lower key engaging pin segments and upper drive pin segments have a line of separation between the segments which is normally displaced from the sheer zone of the plug, but is positioned by the proper key so that the line of separation of all of the pin tumblers align with the plug sheer line and permits rotation of the plug. Such pin tumbler type cylinder locks have been particularly susceptible to the above described types of picking techniques, and many attempts have been made to provide them with resistance to such picking attack. In some cases, the pin tumblers have been so constructed that tampering by picking techniques applied to any one of the tumbler pins automatically locks the remaining tumblers against further movement, or additional recesses have been provided in the outer body or casing so that after a pin tumbler has been picked it re-engages in the absence of clearance of the remaining pin tumbler. Lock-out devices have also been provided so that attempts to pick one or more of the pin tumblers results in additional locking pins being activated to lock the plug against rotation even by authorized persons with a proper key.
To increase resistance to picking by the techniques which are successful with pin tumbler type cylinder locks, cylinder locks of the rotary disc tumbler type have come into wider use. A popular type of rotary disc tumbler cylinder lock is the so-called Abloy lock, wherein a bank of peripherally gated rotary locking discs housed within a rotatable sleeve member have shaped center apertures which respond to a proper key contour surface to align the gates to permit radially inward movement of the locking bar which normally traverses the sheer line between the rotary plug portion and an outer fixed casing of the lock. Such rotary disc tumbler type cylinder locks may be of the general type disclosed in U.S. Pat. Nos. 3,771,340 or 3,848,442 or 3,972,210, with or without related features of other patents obtained by the Finnish corporation Oy Wartsila AB relating to the Abloy lock. Unauthorized detection of the key code or key combination of key-operated cylinder locks of this rotary disc tumbler type has been achieved, however, by techniques such as introducing a picking probe or reading tool into the key opening to interpose an offset shaped extension or feeler thereof between the faces of successive rotary disc tumblers and manipulating the probe or reading tool to detect the position of the peripheral gates on the disc tumblers, signifying the key or combination code, and by observing the angular position of the probe externally of the lock and determining therefrom the key combination of shaped surface contour of the key for that lock. Also, techniques of torquing the cylinder or plug of such locks in a special manner to distort metal from some of the lock components into normally vacant spaces within the lock by application of strong torquing forces to the cylinder or plug have resulted in unauthorized penetration of the lock.
It has been proposed in U.S. patent application Ser. No. 681,241 filed Apr. 28, 1976 by Harry C. Miller et al to specially construct locks of this rotary disc tumbler type so as to provide barriers resisting radially outward movement of the feeler of such a probe or reading tool through the space between adjacent rotary disc tumblers to the zone of the peripheral gates by providing a barrier to penetration of the feeler of such a probe between each of the rotary disc cylinders, as by shaping the confronting faces of adjacent rotary disc tumblers to provide a labyrinth-type passage therebetween. While such a lock, if the rotary disc tumblers are carefully constructed to very close tolerances, may provide effective protection against unauthorized detection of the lock combination or key contour by such reading probe techniques, it is difficult to maintain the space between adjacent tumblers at such small dimensions that effective probe penetration is resisted when the rotary disc tumblers are made to customary manufacturing tolerances.
An object of the present invention, therefore, is the provision of a novel rotary plug cylinder lock having rotary disc type tumblers constructed in a special manner to provide labyrinth-type passages between adjacent tumblers for resisting unauthorized detection of the key combination by reading probe techniques and the like, wherein means are provided for adjusting the spacing between successive disc tumblers in assembled stacks of tumblers in the lock to small dimensions by means of an adjusting set screw to control the labyrinth spacing between successive adjacent disc tumblers and to control spacing of the disc tumblers relative to the key bit positions to improve reliability and performance of the lock.
Another object of the present invention is the provision of a novel rotary plug lock of the rotary disc tumbler type as described in the immediately preceding paragraph, wherein wavy shaped spacers or washers are provided between successive disc tumblers resiliently biasing them to a predetermined spacing between successive disc tumblers, and wherein the set screw adjusting means applies compressive force to the stack of disc tumblers to reduce or control the spacing between successive tumblers, to enable reliable operation and high security performance in dirty environments and avoid dirt-interference operation of adjacent disc tumblers by dirt penetrating intertumbler spaces.
Another object of the present invention is the provision of a novel rotary plug lock of the type described in either of the two immediately preceding paragraphs, wherein an elongated cylindrical guide pin extends forwardly from the rear of the lock to the key entrance thereof along the center axis of the stack of rotary disc tumblers substantially filling an opening therefor and providing a keyway of arcuately curved substantially semi-circular cross-sectional configuration surrounding a portion of the periphery of the guide pin, and wherein the guide pin bears forwardly against the rearmost disc tumbler of the stack and is adjustable axially for adjusting the spaces between successive tumblers.
Yet another object of the present invention is the provision of a rotary plug lock of the type described in the preceding paragraphs, wherein a frangible fence means is provided in an economical manner having two circumferentially spaced thin frangible stop ribs to protect between the sleeve portion of the plug surrounding the stack of rotary disc tumblers and into sector recesses in the periphery of the disc tumblers to readily destruct upon torquing of the plug beyond a certain torque threshold and render the plug inoperable and in locked condition, and yet which does not accidentally destruct or become damaged under normal operation.
Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention.